Short-term effect of atrial fibrillation on atrial contractile function in humans

Atrial structural remodeling and atrial fibrillation substrate: A histopathological perspective

Atrial fibrillation (AF) substrate progresses with the advancement of atrial structural remodeling, resulting in AF perpetuation and recurrence. Although fibrosis is considered a hallmark of atrial structural remodeling, the histological background has not been fully elucidated because obtaining atrial specimens is difficult, especially in patients not undergoing open-heart surgery. Bipolar voltage reduction evaluated using electroanatomic mapping during AF ablation is considered a surrogate marker for the progression of structural remodeling; however, histological validation is lacking. We developed an intracardiac echocardiography-guided endomyocardial atrial biopsy technique to evaluate atrial structural remodeling in patients undergoing catheter ablation for nonvalvular AF. The histological factors associated with a decrease in bipolar voltage were interstitial fibrosis, as well as an increase in myocardial intercellular space preceding fibrosis, myofibrillar loss, and a decrease in cardiomyocyte nuclear density, which is a surrogate marker for cardiomyocyte density. Cardiomyocyte hypertrophy is closely associated with a decrease in cardiomyocyte nuclear density, suggesting that hypertrophic changes compensate for cardiomyocyte loss. Electron microscopy also revealed that increased intercellular spaces indicated the leakage of plasma components owing to increased vascular permeability. Additionally, amyloid deposition was observed in 4 % of biopsy cases. Only increased intercellular space and interstitial fibrosis were significantly higher for long-standing persistent AF than for paroxysmal AF and associated with recurrence after AF ablation, suggesting that this interstitial remodeling is the AF substrate. An increase in intercellular space that occurs early in AF formation is a therapeutic target for the AF substrate, which prevents irreversible interstitial degeneration due to collagen accumulation. This endomyocardial atrial biopsy technique will allow the collection of atrial tissue from a wide variety of patients and significantly facilitate the elucidation of the mechanisms of atrial cardiomyopathy, structural remodeling, and AF substrates.

Left atrial function of patients with atrial fibrillation undergoing thoracoscopic hybrid ablation

OBJECTIVES

Thoracoscopic hybrid ablation is an effective and safe rhythm control strategy for patients with complex forms of atrial fibrillation. Its effect on left atrial function has not yet been studied.

METHODS

In a retrospective single-centre analysis of patients undergoing thoracoscopic hybrid ablation, the left atrial emptying fraction was calculated using the biplane modified Simpson method in the apical 2- and 4-chamber views on transthoracic echocardiography. Left atrial strain (reservoir, conduction and contractility) was quantified using dedicated software.

RESULTS

Sixty-seven patients were included (mean age 64 years, long-standing persistent atrial fibrillation in 69%, median atrial fibrillation history duration 64 months). At baseline, left atrial function and contractility were poor. The reservoir and contractile strain improved postprocedure compared to baseline [15 (standard deviation (SD): 8) and 17 (SD: 6); P = 0.013; 3 (SD: 5) and 4 (SD: 4), P = 0.008], whereas the left atrial volume indexed to the body surface area was reduced [51 ml/m2 (SD: 14) and 47 ml/m2 (SD: 18), P = 0.0024]. In patients with preoperative (long-standing) persistent atrial fibrillation and in patients with rhythm restoration, improvements in the emptying fraction, (reservoir and contractile) strain and the left ventricular ejection fraction were observed, whereas the left atrial volume decreased (P < 0.05).

CONCLUSIONS

In this cohort of patients with severely diseased left atria, improvement in left atrial contractility and in the emptying fraction after thoracoscopic hybrid ablation for atrial fibrillation in patients with persistent atrial fibrillation is mainly due to rhythm restoration. Interestingly, the procedure itself also results in improved left atrial reservoir strain and reversed left atrial remodelling by reducing left atrial volume.

Sacubitril/Valsartan Cannot Improve Cardiac Function Compared with Valsartan in Patients Suffering Nonvalvular Atrial Fibrillation without Systolic Heart Failure

This study investigates the effect of sacubitril/valsartan (Sac/Val) in patients diagnosed with nonvalvular atrial fibrillation (AF) without systolic heart failure (SHF).Nonvalvular AF patients without SHF admitted to the People's Hospital of Bortala Mongol Autonomous Prefecture from December 2020 to December 2021 were enrolled and randomly divided into Sac/Val treatment group (group T) and valsartan treatment group (group C, control). For subgroup analysis, patients were divided into subgroups with and without diastolic heart failure (DHF). After 1-month adaptive phase and subsequent 3-month treatment period, patients were followed up in the cardiology clinic. Plasma levels of biochemical markers and echocardiographic parameters before and after treatment were evaluated, and DHF scores were computed to assess diastolic function.Of 61 enrolled patients, 46 patients completed follow-up. Sac/Val treatment did not increase the percentage of sinus rhythm. Although N-terminal pro-B-type natriuretic peptide (NT-proBNP) expression tended to be reduced in both groups after 3 months of treatment, the differences compared with respective baseline levels and between groups were not significant. According to subgroup analysis, although NT-proBNP expression in the subgroup with DHF was lower at follow-up compared to baseline, the difference was not statistically significant. Similarly, no marked differences in echocardiographic parameters or tissue Doppler parameters related to DHF were detected between the groups (P > 0.05). Additionally, a subgroup analysis found no significant variations in the echocardiographic measures (P > 0.05).Sac/Val is not superior to valsartan for the short-term treatment of patients suffering with AF without SHF in improving NT-proBNP level and cardiac function.

Upstream Therapy for Atrial Fibrillation Prevention: The Role of Sacubitril/Valsartan

The therapy or prevention of atrial fibrillation (AF) is defined as upstream therapy when conducted with the use of drugs, e.g., angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor antagonists, statins, and omega-3 fatty acids, not included in the classes of antiarrhythmic drugs recognized by the Vaughan Williams classification. In our review, we illustrate the rational bases of upstream AF therapy, which encompasses drugs having the property to reduce hemodynamic congestion and cardiac overload, as in the case of ACEIs or angiotensin receptor blockers, as well as drugs able to prevent atrial fibrosis or reduce oxidative stress, such as statins or omega-3 fatty acids, respectively. In this review, randomized controlled trials (RCTs) conducted with the abovementioned drugs are examined. Really, these RCTs have generated mixed results. In the context of the prevention and therapy of AF, our experience is then presented, relating to a patient with heart failure and reduced left ventricular ejection fraction, with a history of relapsing episodes of paroxysmal AF. In this patient, administration of sacubitril/valsartan at appropriate doses allowed recovery of the sinus rhythm. Therefore this case testifies how the upstream therapy of AF might have good results when conducted with sacubitril/valsartan. Thus, RCTs with adequate statistical power are warranted in order to confirm the preliminary encouraging result of our case report, and validate a useful role of sacubitril/valsartan as an upstream therapy of AF.

Atrial electromechanical delay assessment in early phase after catheter ablation for patients with atrial fibrillation

BACKGROUND

Variation of atrial electromechanical delay (AED) in early phase after catheter ablation in patients with atrial fibrillation (AF) is lacking.

METHODS

Fifty-five consecutive patients restored sinus rhythm after ablation was included. Echocardiography was performed at 4 h, 1 day, and 3 days after radiofrequency catheter ablation, and AED was measured simultaneously by echocardiography with pulse Doppler imaging and pulse wave tissue Doppler imaging.

RESULTS

AED parameters were significantly longer in the nonparoxysmal atrial fibrillation (NPAF) group than in the paroxysmal atrial fibrillation (PAF) group at each checking point after ablation (P < 0.05). Compared with other checking points, AED parameters were significantly longer 4 h postablation in the NPAF group, while no significant difference was found between different checking points in the PAF group. AED-leap, representing the variation of AED in NPAF patients, was significantly positively correlated with the duration of NPAF (r = 0.5291, P = 0.0113).

CONCLUSIONS

Compared with PAF, NPAF patients have a longer AED postablation, and an abrupt decrease in the initial-h postablation. Such phenomenon gives rise to the different clinical features of PAF and NPAF, and could guide different assessment and treatment strategies for different types of AF.

Correlation between plasma brain natriuretic peptide levels and left atrial appendage flow velocity in patients with non-valvular atrial fibrillation and normal left ventricular systolic function

BACKGROUND

The left atrial appendage (LAA) flow velocity is an important factor for thrombus formation in patients with non-valvular atrial fibrillation (NV-AF). Recently, the relation of plasma brain natriuretic peptide (BNP) levels and thromboembolism has been reported in patients with NV-AF. The aim of this study was to determine whether the plasma BNP is predictive of lower LAA flow velocity in patients with NV-AF and normal left ventricular (LV) systolic function.

METHODS AND RESULTS

A total of 184 patients with NV-AF (132 men; 65 ± 12 years, LV ejection fraction; 65 ± 10%) underwent transthoracic echocardiography, transesophageal echocardiography (TEE), and measurement of plasma BNP. The LAA flow velocity was obtained by pulsed Doppler TEE. Multivariate logistic regression analysis demonstrated that plasma BNP levels, left atrial volume index (LAVI), LV mass index (LVMI), and the CHADS₂ score were independent predictors of lower LAA flow velocity (< 20 cm/s). Plasma BNP levels (r = - 0.58, p < 0.001) were correlated with LAA flow velocity. The area under the curve (AUC) for BNP (AUC 0.803) was larger than that for the CHADS₂ score (AUC 0.712), LAVI (AUC 0.664) and LVMI (AUC 0.608) with an optimal BNP cut-off value of 164 pg/ml (sensitivity 75.7%, specificity 71.1%).

CONCLUSIONS

This study showed that a higher plasma BNP was associated with a lower LAA flow velocity in patients with NV-AF and normal LV systolic function. The plasma BNP may complement the role of the CHADS₂ score in predicting lower LAA flow velocity.

Intermittent vs. Continuous Anticoagulation theRapy in patiEnts with Atrial Fibrillation (iCARE-AF): a randomized pilot study

PURPOSE

We hypothesized that intermittent anticoagulation based on daily rhythm monitoring using the novel oral anticoagulants (NOACs) is feasible and safe among patients with paroxysmal atrial fibrillation (AF).

METHODS

Patients with paroxysmal AF and ≥1 risk factors for stroke were randomized to either intermittent or continuous anticoagulation. Those in the intermittent group were instructed to transmit a daily ECG using an iPhone-based rhythm monitoring device. If AF was detected, patients received one of the NOACs for 48 h-1 week. Patients who failed to transmit an ECG for three consecutive days or more than 7 days total were crossed over to continuous anticoagulation. Patients in the continuous group received one of the NOACs.

RESULTS

Fifty-eight patients were randomized to either intermittent (n = 29) or continuous anticoagulation (n = 29). Over a median follow-up of 20 months, 20 patients in the intermittent group failed to submit a daily ECG at least once (median three failed submissions). Four patients (14 %) crossed over to continuous anticoagulation due to failure to submit an ECG for three consecutive days. One stroke (continuous group) occurred during the study. Major bleeding occurred in two patients in the continuous and one patient in the intermittent group, after crossing over to continuous anticoagulation. In a prespecified per-protocol analysis, gastrointestinal bleeding was more frequent in the continuous group (16 vs. 0 %; p = 0.047).

CONCLUSIONS

Intermittent anticoagulation based on daily rhythm monitoring is feasible and may decrease bleeding in low-risk patients with paroxysmal AF. A larger trial, adequately powered to detect clinical outcomes, is warranted.

Absence of left atrial stunning after cardioversion of recent-onset atrial fibrillation in patients at low-stroke risk

OBJECTIVE

The aim of the present study was to evaluate the presence and degree of spontaneous echo contrast (SEC) in the left atrium and of left atrial appendage (LAA) contractility before and after cardioversion (CV) in patients with recent-onset atrial fibrillation (AF).

METHODS

Our study included 56 patients divided into two groups: group 1, comprising 32 clinically stable patients who were admitted to the Emergency Department with less than or equal to 48 h duration AF, and who underwent transoesophageal echocardiography (TEE)-guided CV; and the control group (group 2), comprising 24 patients admitted to the Cardiological Department for elective TEE-guided CV of greater than 48 h AF. All patients underwent repeat TEE within 1 h after successful CV.

RESULTS

Patients with recent-onset AF (group 1) showed no thrombogenic milieu at baseline without any evidence of atrial stunning after successful CV. SEC mean grade (0-3 grading) was 0.09±0.3 versus 0.12±0.4 after CV (P=0.98), and LAA flow velocity was 60.7±19.4 versus 56.7±20.5 cm/s after CV (P=0.07). Group 2 patients showed a significantly higher degree of SEC compared with those in group 1 (0.09±0.3 vs. 0.66±0.7, P=0.0093) and significantly lower LAA flow velocities (60.7±19.4 vs. 32.5±12.4, P<0.0001), with significant worsening after successful CV (SEC degree: 0.66±0.9 vs. 1.37±0.9, P=0.0093; LAA flow velocity: 32.5±12.4 vs. 20.4±12.7 cm/s, P<0.0001).

CONCLUSION

The absence of thrombogenic milieu and of left atrial stunning after CV in patients with recent-onset AF favours early CV without anticoagulation, at least in patients with a low thromboembolic risk profile. These patients could be discharged earlier from urgent care.

Role of tumor necrosis factor alpha in the pathogenesis of atrial fibrillation: A novel potential therapeutic target?

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice and a major cause of morbidity and mortality. Although the fundamental mechanisms underlying AF remain incompletely understood, atrial remodeling, including structural, electrical, contractile, and autonomic remodeling, has been demonstrated to contribute to the substrate for AF maintenance. Accumulating evidence shows that tumor necrosis factor alpha (TNF-α) plays exceedingly important roles in atrial remodeling. This article reviews recent advances in the roles of TNF-α in the pathogenesis of AF, elucidates the related mechanisms, and exploits its potential usefulness as a novel therapeutic target.

Cardioversion of uncomplicated paroxysmal atrial fibrillation: a survey of practice by Canadian emergency physicians

Objective:

Paroxysmal atrial fibrillation (PAF) is the rhythm disturbance most commonly encountered by emergency physicians, yet the role played by emergency physicians in the management of this condition has not been well described. The purpose of this study was to describe the management of uncomplicated PAF by Canadian emergency physicians.

Methods:

All members of the Canadian Association of Emergency Physicians with a Canadian address (n = 1255) were mailed a 15-point questionnaire regarding training/certification, hospital demographics and practice patterns regarding the management of uncomplicated PAF. Chisquared analysis and Fisher’s Exact test were performed to identify significant differences in reported practice patterns in relation to demographic variables. Significant associations were tested for interaction using the Mantel–Haenszel test.

Results:

We received 663 responses, representing a 52.8% response rate. Six hundred and twenty-two (95%), 514 (78%) and 242 (38%) respondents reported routine performance of rate control, chemical cardioversion and electrical cardioversion respectively. Physicians working in high-volume emergency departments (&gt;50 000 visits/yr) were significantly more likely to self-manage rate control and chemical/electrical cardioversion than those working in lower volume emergency departments. Residency training was associated with higher performance of electrical (44% v. 31%, p &lt; 0.01) but not chemical cardioversion or rate control, although, amongst residency trained physicians, those with FRCP-level training were significantly more likely to perform both chemical (86% v. 76%, p &lt; 0.05) and electrical (57% v. 37%, p &lt; 0.01) cardioversion.

Conclusion:

Canadian emergency physicians surveyed in this study actively manage uncomplicated PAF. We found significant variations in practice, especially related to the use of electrical cardioversion. This may reflect different practice environments, levels of training, and lack of evidence to guide best practice. Further research is required to determine the optimal care of PAF in the emergency department setting.

External Cardioversion of Atrial Fibrillation Causes an Early Improvement of Cardiac Performance: A Longitudinal Strain Analysis Study

Introduction:

Atrial fibrillation (AF) is often associated with heart failure. Several studies have demonstrated that resumption of sinus rhythm (SR) improves cardiac output in the long-term. Aims of this study were to evaluate the acute variations of left ventricular (LV) performance, following successful external cardioversion (ECV) of persistent AF using longitudinal strain (LSt) analysis, and the influence of inflammation.

Materials and Methods:

We enrolled 48 patients with AF (age: 73 ± 12 years, men: 83.3%). A standard transthoracic echocardiographic evaluation was performed before the procedure and 6 h later; this included the analysis of LV endocardial peak LSt, a measure of myocardial deformation. In the last 32 patients, plasma concentration of interleukin-6 (IL-6) was also determined.

Results:

Restoration of SR led to the decrease of heart rate (HR) (74 ± 21 vs 64 ± 10 bpm, P < 0.001) and LV end-systolic volume (30 ± 16 vs 27 ± 17 mL/m², P = 0.001), and to the increase of LV end-diastolic volume (LVEDV) (56 ± 20 vs 60 ± 21 mL/m², P = 0.036) and ejection fraction (EF) (48 ± 10 vs 57 ± 11%, P < 0.001). Peak LSt improved in 43 (89.6%) patients (-12.9 ± 3.3 vs -18.0 ± 4.7%, P < 0.001). Multivariate analysis (R = 0.729, P < 0.001) showed that strain changes were directly correlated with basal HR and the appearance of atrial mechanical activity and inversely correlated with corrected thyroid dysfunction, LVEDV and the presence of a permanent pacemaker. Higher levels of IL-6 negatively affected LV performance improvement.

Conclusions:

Effective ECV of AF determines a significant and fast improvement of LV performance, which is readily captured by LSt analysis. Inflammatory status may impact the response to SR restoration.

Chronic atrial fibrillation causes left ventricular dysfunction in dogs but not goats: experience with dogs, goats, and pigs

Structural remodeling in chronic atrial fibrillation (AF) occurs over weeks to months. To study the electrophysiological, structural, and functional changes that occur in chronic AF, the selection of the best animal model is critical. AF was induced by rapid atrial pacing (50-Hz stimulation every other second) in pigs (n = 4), dogs (n = 8), and goats (n = 9). Animals underwent MRIs at baseline and 6 mo to evaluate left ventricular (LV) ejection fraction (EF). Dogs were given metoprolol (50-100 mg po bid) and digoxin (0.0625-0.125 mg po bid) to limit the ventricular response rate to <180 beats/min and to mitigate the effects of heart failure. The pacing leads in pigs became entirely encapsulated and lost the ability to excite the heart, often before the onset of sustained AF. LV EF in dogs dropped from 54 ± 11% at baseline to 33 ± 7% at 6 mo (P < 0.05), whereas LV EF in goats did not drop significantly (69 ± 8% at baseline vs. 60 ± 9% at 6 mo, P = not significant). After 6 mo of AF, fibrosis levels in dog atria and ventricles increased, whereas only atrial fibrosis levels increased in goats compared with control animals. In our experience, the pig model is not appropriate for chronic rapid atrial pacing-induced AF studies. Rate-controlled chronic AF in the dog model developed HF and LV fibrosis, whereas the goat model developed only atrial fibrosis without ventricular dysfunction and fibrosis. Both the dog and goat models are representative of segments of the patient population with chronic AF.

Effects of different small HSPB members on contractile dysfunction and structural changes in a Drosophila melanogaster model for Atrial Fibrillation

The most common clinical tachycardia, Atrial Fibrillation (AF), is a progressive disease, caused by cardiomyocyte remodeling, which finally results in contractile dysfunction and AF persistence. Recently, we identified a protective role of heat shock proteins (HSPs), especially the small HSPB1 member, against tachycardia remodeling in experimental AF models. Our understanding of tachycardia remodeling and anti-remodeling drugs is currently hampered by the lack of suitable (genetic) manipulatable in vivo models for rapid screening of key targets in remodeling. We hypothesized that Drosophila melanogaster can be exploited to study tachycardia remodeling and protective effects of HSPs by drug treatments or by utilizing genetically manipulated small HSP-overexpressing strains. Tachypacing of Drosophila pupae resulted in gradual and significant cardiomyocyte remodeling, demonstrated by reduced contraction rate, increase in arrhythmic episodes and reduction in heart wall shortening, compared to normal paced pupae. Heat shock, or pre-treatment with HSP-inducers GGA and BGP-15, resulted in endogenous HSP overexpression and protection against tachycardia remodeling. DmHSP23 overexpressing Drosophilas were protected against tachycardia remodeling, in contrast to overexpression of other small HSPs (DmHSP27, DmHSP67Bc, DmCG4461, DmCG7409, and DmCG14207). (Ultra)structural evaluation of the tachypaced heart wall revealed loss of sarcomeres and mitochondrial damage which were absent in tachypaced DmHSP23 overexpressing Drosophila. In addition, tachypacing induced a significant increase in calpain activity, which was prevented in tachypaced Drosophila overexpressing DmHSP23. Tachypacing of Drosophila resulted in cardiomyocyte remodeling, which was prevented by general HSP-inducing treatments and overexpression of a single small HSP, DmHSP23. Thus, tachypaced D. melanogaster can be used as an in vivo model system for rapid identification of novel targets to combat AF associated cardiomyocyte remodeling.

Differential gene expression during atrial structural remodeling in human left and right atrial appendages in atrial fibrillation

Extracellular matrix (ECM) remodeling increases the vulnerability to atrial fibrillation (AF). Some gene expressions are crucial for the metabolism of ECM. The left atrium plays an important role in maintaining AF. However, most studies investigated only the right atrial tissue. We therefore chose human tissue samples from both the left and right atrial to detect the different gene expressions during structural remodeling in AF. The atrial appendages tissue samples from 24 patients with chronic AF and 12 patients with sinus rhythm were obtained when they were undergoing mitral/aortic valve replacement operation. The mRNA levels of matrix metalloproteinases-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), disintegrin, metalloproteases-15, and integrins β1 were determined by reverse transcription-polymerase chain reaction (RT-PCR). In AF group, the level of MMP-9 in left atrial appendage (LAA) was increased (P< 0.001), while integrin β1 level was decreased (P< 0.05) compared with those expressed in right atrial appendage (RAA) tissue. The levels of disintegrin, metalloproteinases-15, and TIMP-1 genes in the LAA and RAA had no significant differences. The results demonstrated that the gene expressions in the LAA and RAA are different during AF, which implied that the mechanism of atrial structural remodeling in AF is due to multiple sources and is complicated.

Pathophysiological mechanisms of atrial fibrillation: a translational appraisal

Atrial fibrillation (AF) is an arrhythmia that can occur as the result of numerous different pathophysiological processes in the atria. Some aspects of the morphological and electrophysiological alterations promoting AF have been studied extensively in animal models. Atrial tachycardia or AF itself shortens atrial refractoriness and causes loss of atrial contractility. Aging, neurohumoral activation, and chronic atrial stretch due to structural heart disease activate a variety of signaling pathways leading to histological changes in the atria including myocyte hypertrophy, fibroblast proliferation, and complex alterations of the extracellular matrix including tissue fibrosis. These changes in electrical, contractile, and structural properties of the atria have been called "atrial remodeling." The resulting electrophysiological substrate is characterized by shortening of atrial refractoriness and reentrant wavelength or by local conduction heterogeneities caused by disruption of electrical interconnections between muscle bundles. Under these conditions, ectopic activity originating from the pulmonary veins or other sites is more likely to occur and to trigger longer episodes of AF. Many of these alterations also occur in patients with or at risk for AF, although the direct demonstration of these mechanisms is sometimes challenging. The diversity of etiological factors and electrophysiological mechanisms promoting AF in humans hampers the development of more effective therapy of AF. This review aims to give a translational overview on the biological basis of atrial remodeling and the proarrhythmic mechanisms involved in the fibrillation process. We pay attention to translation of pathophysiological insights gained from in vitro experiments and animal models to patients. Also, suggestions for future research objectives and therapeutical implications are discussed.

Surface ECG organization time course analysis along onward episodes of paroxysmal atrial fibrillation

The complete understanding of the mechanisms leading to the initiation, maintenance and self-termination of atrial fibrillation (AF) still is an unsolved challenge for cardiac electrophysiology. Studies in which AF has been induced have shown that electrophysiological and structural remodeling of the atria during the arrhythmia could play an important role in the transition from paroxysmal to persistent AF. However, to this day, the time course of the atrial remodeling along onward episodes of non-induced paroxysmal AF has not been investigated yet. In this work, a non-invasive method, based on the regularity estimation of AF through sample entropy (SampEn), has been used to assess the organization evolution along onward episodes of paroxysmal AF. Given that AF organization has been associated to the number of existing wavelets wandering throughout the atrial tissue, SampEn could be considered as a concomitant estimator of atrial remodeling. The achieved results, in close agreement with previous findings obtained from invasive recordings, proved several relevant aspects of arial remodeling. Firstly, a progressive disorganization increase (SampEn increase) along onward episodes of AF has been observed for 63% of the analyzed patients, whereas a stable AF organization degree has been appreciated in the remaining 37%. Next, a positive correlation between episode duration and SampEn has been obtained (R=0.541, p<0.01). Finally, a remarkable influence of the fibrillation-free interval, preceding each episode, on the corresponding level of AF organization at the onset of the subsequent AF episode has been observed, with a correlation between these two indices of R=0.389 (p<0.01). As a consequence, it could be considered that atrial electrophysiological dynamics that occur along onward paroxysmal AF episodes are reflected and can be quantified from ECG recordings through non-invasive organization estimation.

Noninvasive organization analysis along consecutive episodes of paroxysmal atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. Although its mechanisms are incompletely understood, electrophysiological and structural remodeling of the atria seem to play an important role in the arrhythmia transition from paroxysmal to persistent. However, the time course of the atrial remodeling along onward episodes of non-induced paroxysmal AF has not been investigated yet. In this work, a non-invasive method, based on the regularity estimation of AF through sample entropy (SampEn), has been used to assess the organization evolution along onward episodes of paroxysmal AF. Given that AF organization has been associated to the number of existing wavelets wandering throughout the atrial tissue, SampEn could be considered as a concomitant estimator of atrial remodeling. The achieved results, in close agreement with previous findings obtained from invasive recordings, showed a progressive disorganization increase along onward episodes of AF for 63% of the analyzed patients and a stable AF organization degree in the remaining 37%. Additionally, a positive correlation between episode duration and SampEn was also noticed (R = 0.541, p < 0.01). As a consequence, it could be considered that atrial electrophysiological dynamics that occur along onward paroxysmal AF episodes are reflected and can be quantified from ECG recordings through non-invasive organization estimation.

Candesartan decreases type III procollagen-N-peptide levels and inflammatory marker levels and maintains sinus rhythm in patients with atrial fibrillation

This study has evaluated whether candesartans prevent the recurrence of atrial fibrillation (AF) and decrease type III procollagen-N-peptide (PIIINP) levels. A total of 153 patients with AF were enrolled in this study. Three groups of patients were compared; candesartan group was treated with candesartan plus bepridil (n = 52); and carvedilol group with carvedilol plus bepridil (n = 51); and bepridil group with bepridil alone (n = 50). The primary end point was length of time to the recurrence of AF and all patients were ultimately followed-up for 730 days. Serum levels of the biomarkers were measured at baseline and after 24 months. Maintenance of sinus rhythm was achieved in 25 (50%) patients in bepridil group, 37 (73%) in candesartan group, and 34 (67%) in carvedilol group, giving a bepridil group/candesartan group hazard ratio of 0.36 (95% confidence interval 0.21-0.63; P = 0.03). Candesartan significantly decreased PIIINP levels at 24 months than at baseline in sinus rhythm group (0.57 +/- 0.02 vs. 0.64 +/- 0.05 U/mL, P = 0.04) and did not decrease PIIINP levels in the recurrence group. In conclusions, PIIINP might be related to the possibility of the atrial fibrosis for AF. However, further studies are needed to clarify the relationship between PIIINP and AF.

Digitalis does not improve left atrial mechanical dysfunction after successful electrical cardioversion of chronic atrial fibrillation

This study was designed to investigate whether administration of digitalis could improve mechanical function of left atrial appendage (LAA) and left atrium prospectively in patients with atrial stunning. Fifty-four consecutive patients in whom atrial stunning was observed immediately after cardioversion of chronic atrial fibrillation (AF) were randomized into digitalis or control group for 1 week following cardioversion. Transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) were performed prior to, immediately following, 1 day after and 1 week after cardioversion to measure transmitral flow velocity and LAA flow velocity. Electrical cardioversion of AF elicited significantly slower left atrial appendage peak emptying velocity (LAA-PEV) and peak filling velocity (LAA-PFV) immediately following cardioversion in both groups. 1 day post cardioversion, there were no significant differences in transmitral E wave, A wave, E/A ratio, LAA-PEV, LAA-PFV or left atrial appendage ejection fraction (LAA-EF) between digitalis and control groups. 1 week post cardioversion, no significant differences were found in transmitral E wave, A wave, E/A ratio, LAA-PEV, LAA-PFV or LAA-EF between the two groups. The occurrence rates of spontaneous echo contrast were not significantly different between digitalis and control groups one day and one week post cardioversion. In conclusion, digitalis did not improve left atrial and appendage mechanical dysfunction following cardioversion of chronic AF. Digitalis did not prevent the development of spontaneous echo contrast in left atrial chamber and appendage. This may be due to the fact that digitalis aggravates intracellular calcium overload induced by chronic AF and has a negative effect on ventricular rate.

Valsartan for prevention of recurrent atrial fibrillation

BACKGROUND

Atrial fibrillation is the most common cardiac arrhythmia, and no current therapy is ideal for control of this condition. Experimental studies suggest that angiotensin II-receptor blockers (ARBs) can influence atrial remodeling, and some clinical studies suggest that they may prevent atrial fibrillation.

METHODS

We conducted a large, randomized, prospective, placebo-controlled, multicenter trial to test whether the ARB valsartan could reduce the recurrence of atrial fibrillation. We enrolled patients who were in sinus rhythm but had had either two or more documented episodes of atrial fibrillation in the previous 6 months or successful cardioversion for atrial fibrillation in the previous 2 weeks. To be eligible, patients also had to have underlying cardiovascular disease, diabetes, or left atrial enlargement. Patients were randomly assigned to receive valsartan or placebo. The two primary end points were the time to a first recurrence of atrial fibrillation and the proportion of patients who had more than one recurrence of atrial fibrillation over the course of 1 year.

RESULTS

A total of 1442 patients were enrolled in the study. Atrial fibrillation recurred in 371 of the 722 patients (51.4%) in the valsartan group, as compared with 375 of 720 (52.1%) in the placebo group (adjusted hazard ratio, 0.97; 96% confidence interval [CI], 0.83 to 1.14; P=0.73). More than one episode of atrial fibrillation occurred in 194 of 722 patients (26.9%) in the valsartan group and in 201 of 720 (27.9%) in the placebo group (adjusted odds ratio, 0.89; 99% CI, 0.64 to 1.23; P=0.34). The results were similar in all predefined subgroups of patients, including those who were not receiving angiotensin-converting-enzyme inhibitors.

CONCLUSIONS

Treatment with valsartan was not associated with a reduction in the incidence of recurrent atrial fibrillation. (ClinicalTrials.gov number, NCT00376272.)

Effect of verapamil on prevention of atrial fibrillation in patients implanted with an implantable atrial defibrillator

BACKGROUND

The role of verapamil in the prevention of atrial fibrillation (AF) in patients with recurrent AF is unknown.

HYPOTHESIS

The aim of this study was to evaluate the effect of verapamil on the prevention of AF in patients implanted with an implantable atrial defibrillator (IAD).

METHODS

The effects of verapamil (240 mg/day) on the total duration of AF, number of AF recurrences, and number of cardioversions were prospectively evaluated in a randomized, crossover fashion over an 8-week period in 11 patients (9 men, 2 women; mean age: 60 +/- 6 years) implanted with an IAD.

RESULTS

Implantable atrial defibrillators successfully converted 13 of 14 (93%) spontaneous episodes of AF. There was no significant difference in the efficacy of cardioversion (86 vs. 100%, p = 0.8), the total duration of AF (173 +/- 198 vs. 270 +/- 241 h, p = 0.5), the number of AF episodes (8.5 +/- 9.0 vs. 9.3 +/- 10.2, p = 0.3), and the number of cardioversions (1.7 +/- 2.4 vs. 1.8 +/- 2.1 p = 0.7) with or without treatment with verapamil.

CONCLUSIONS

The results of the present study suggest that treatment with verapamil has no significant effect on the prevention of AF in patients treated with an LAD.

Atrial Septal Defect and Atrial Fibrillation: The Known and Unknown

Atrial fibrillation (AF) is a common complication in patients with atrial septal defects (ASDs). The link between AF and ASD is fairly complex and entails modifications in electrophysiologic, contractile and structural properties, at the cellular and tissue level, of both atria, mainly due to chronic atrial stretch and dilation. Surgical repair or percutaneous closure of ASDs are equally effective in reducing mortality and symptoms but limited in preventing or curbing AF, unless combined with an arrhythmia-specific procedure. Transesophageal echocardiography (TEE) and intracardiac echocardiography (ICE) have improved the safety and success of the above procedures. Finally, clearer understanding of the pathophysiology of AF in patients with ASD (and CHF, in general) has led to target-specific advances in medical management.

Mitral annular velocity by Doppler tissue imaging for the evaluation of atrial stunning after cardioversion of atrial fibrillation

OBJECTIVE

Atrial and/or appendage stunning (AS) usually occur after successful cardioversion of atrial fibrillation (AF). Several parameters except mitral annular velocity were previously evaluated to determine AS. We investigated whether mitral annular velocity was useful for determining of AS.

METHODS

This study consisted of 52 consecutive patients with AF <3 months who converted to the sinus rhythm. Mitral inflow and annular velocities were measured before and after cardioversion. Left atrial appendage (LAA) size and flow were assessed. The average velocity of septal and lateral segments of mitral annulus was considered as the final annular velocity. Thrombus and/or spontaneous echo contrast (SEC) were also investigated.

RESULTS

Of 52 patients, 29 (56%) had AS but 23 did not. There was no significant difference in age, gender, and cardioversion type between two groups. Hypertension was more prevalent in patients without AS compared to those with AS (P = 0.02). Mitral annular systolic and E-wave velocities were comparable in both groups (P > 0.05). Mitral annular A-wave velocity (3.1 +/- 2.9 vs. 7.1 +/- 2.2 cm/s, P < 0.001), and its velocity-time integral (0.27 +/- 0.22 vs. 0.74 +/- 0.19 cm, P < 0.001) were significantly lower in patients with AS compared with those without AS. The annular A-wave velocity < or =3.3 cm/s predicted AS with a sensitivity of 59% and specificity of 76%. It was correlated with mitral inflow A velocity (r = 0.85, P < 0.001), LAA emptying velocity (r = 0.41, P = 0.003) and presence of SEC (r = -0.52, P < 0.001).

CONCLUSION

After cardioversion of AF, mitral annular A-wave velocity may be a new marker to determine AS.

NIP-141, a multiple ion channel blocker, terminates aconitine-induced atrial fibrillation and prevents the rapid pacing-induced atrial effective refractory period shortening in dogs

AIMS

NIP-141 is a novel multiple ion channel blocker with atrial selective effects. In this study, we examined the effects of NIP-141 on aconitine-induced atrial fibrillation (AF) and rapid atrial pacing-induced atrial effective refractory period (ERP) shortening in dogs.

METHODS AND RESULTS

Aconitine AF was induced by the application of aconitine on the right appendage. NIP-141 (10 mg/kg) converted AF to sinus rhythm in 5 of 6 dogs. The Na(+) channel blockers disopyramide (1 mg/kg) and phenytoin (10 mg/kg) also terminated AF, but the I(Kr) blocker (d-sotalol; 4 mg/kg) and a Ca(2+) channel blocker (verapamil; 0.3 mg/kg) did not terminate AF in this model. To clarify the mechanism of AF termination, we examined the effects on ERP and conduction time, but NIP-141 (10 mg/kg) had no significant effects. In a short-term rapid atrial pacing model, NIP-141 (2.5 mg/kg/10 min, followed by 0.033 mg/kg/min) prevented atrial ERP shortening. We also found NIP-141 bound to Na(+) channel site 2 receptor and L-type Ca(2+) channel, but not to Na(+) channel site 1 receptor using radioligands binding assay.

CONCLUSION

NIP-141 terminated AF in aconitine-induced AF and prevented the atrial remodelling by short-term rapid pacing in dogs, possibly via the blocking of Na(+) and Ca(2+) channels.

Efficacy of Angiotensin Receptor Blockers in Cardiovascular Disease

The cardiovascular continuum describes the progression of pathophysiologic events from cardiovascular risk factors to symptomatic cardiovascular disease (CVD) and life-threatening events. Pharmacologic intervention early in the continuum may prevent or slow CVD development and improve quality of life. The renin-angiotensin-aldosterone system (RAAS) is central to the pathophysiology of CVD at many stages of the continuum. Numerous clinical trials of angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) have shown that RAAS blockade provides benefits to patients across the continuum. ARBs are as effective as ACE inhibitors in the treatment of hypertension; however tolerability and adherence to therapy appear to be improved with ARBs. Large clinical trials have shown that ARBs may provide therapeutic benefits beyond blood pressure control in patients with diabetes, heart failure or at risk of heart failure following a myocardial infarction. In addition, ARBs have been shown to provide protective effects in patients with impaired renal function or left ventricular hypertrophy. Additional clinical trials are ongoing to further characterize the role of ARBs in CVD management.

Extensive Ablation During Pulmonary Vein Antrum Isolation Has No Adverse Impact on Left Atrial Function: An Echocardiography and Cine Computed Tomography Analysis

BACKGROUND

Although pulmonary vein antrum isolation (PVAI) may cure atrial fibrillation (AF) and improve left atrial (LA) function, the effect of extensive LA ablation on LA function is not well known.

OBJECTIVE

To assess the impact of PVAI on LA function remotely postablation.

METHODS

Consecutive patients undergoing PVAI had either transthoracic (TTE) and transesophageal (TEE) echocardiography (n = 41) or cine EBCT (n = 26) performed preablation and 6 months postablation. Only patients with paroxysmal and persistent, but not permanent, AF were included. Imaging was done in sinus rhythm for all patients. LA diameter (LAD), LA systolic and diastolic areas, and left atrial fractional area change (LFAC) were assessed by TTE. Transmitral (TMF), left atrial appendage (LAA), and pulmonary venous (PVF) Doppler flows were measured by TEE. Peak A on TMF, LAA peak emptying velocity (LAAF), and peak A reversal (AR) on PVF were used as surrogates of LA contractile function. Peak S on PV flow was used as a surrogate of reservoir function. LA areas, volumes, and LA ejection fraction (LAEF) were measured from cine EBCT.

RESULTS

Mean radiofrequency ablation time was 45 +/- 21 minutes. All four PVs were isolated for all patients; there were no cases of PV stenosis. Echocardiography revealed a significant reduction in LAD and LA areas post-PVAI. Both peak A and peak AR were also higher post, while other variables showed strong trends toward improvement. In the subset of patients with persistent AF, post-PVAI improvements were seen in LA size, peak A, and even peak S (P = 0.04). Cine EBCT showed a significant decrease in both LA areas and volumes post-PVAI. There was also a significant improvement in LAEF post-PVAI from 17 +/- 6% to 22 +/- 5% (P = 0.01).

CONCLUSION

Extensive ablation during PVAI does not cause deterioration in LA function, and may cause long-term improvement, especially in patients with higher AF burden.

Rationale and design of the GISSI-Atrial Fibrillation Trial: a randomized, prospective, multicentre study on the use of valsartan, an angiotensin II AT1-receptor blocker, in the prevention of atrial fibrillation recurrence

BACKGROUND

The possibility of preventing atrial fibrillation recurrence with anti-arrhythmic agents is very limited, given the discouraging results obtained with current drugs in many patients. Data from experimental studies suggest that angiotensin II AT1-receptor blockers can influence atrial remodelling, a key factor in atrial fibrillation initiation and maintenance. Moreover, some preliminary clinical data show that angiotensin II AT1 -receptor blockers can prevent atrial fibrillation episodes. The GISSI-Atrial Fibrillation (AF) trial is a randomized, prospective, parallel group, placebo-controlled, multicentre study designed to test whether angiotensin II AT1-receptor blockers can reduce atrial fibrillation recurrence.

OBJECTIVES AND METHODS

The primary objective of the study is to demonstrate that, in patients with a history of recent atrial fibrillation who are treated with the best recommended therapies, the addition of the angiotensin II AT1-receptor blocker valsartan (titrated up to 320 mg) is superior to placebo in reducing atrial fibrillation recurrence. A substudy will analyse the effect of valsartan on left atrial dimensions and on neurohormones. The study population consists of patients with symptomatic atrial fibrillation (at least two electrocardiogram documented atrial fibrillation episodes in the previous 6 months or successful cardioversion in the last 2 weeks) with underlying cardiovascular diseases or comorbidities. With approximately 100 centres participating in Italy, a total of 1402 patients are randomized in a 1 : 1 ratio to receive valsartan or placebo. The enrolment period will last 12 months and the patients will be followed for 12 months from study entry.

CONCLUSIONS

The GISSI-AF is the largest trial aimed at assessing the role of angiotensin receptor blockade in reducing the recurrence of atrial fibrillation and its possible mechanisms of action in terms of its effects on atrium remodelling and neurohormones.

Transthoracic Echocardiographic Predictors of the Left Atrial Appendage Contraction Velocity in Stroke Patients with Sinus Rhythm

Systemic embolization is a potential complication in patients with thrombi situated in the left atrium and particularly, in the left atrial appendage (LAA). Reduced LAA contraction velocities, determined by the transesophageal echocardiography (TEE), are associated with increased risk of LAA spontaneous echocontrast and thrombus formation, and a history of systemic embolism. However, TEE remains a semi-invasive procedure, limiting its serial application as a screening tool. Therefore, it is desirable to obtain information regarding LAA function by transthoracic echocardiography in patients having cardioembolic stroke. The present study was designed to investigate various echocardiographic variables for patients with stroke to predict LAA dysfunction, reflected as reduced LAA contraction velocity. We studied a total of 61 patients with newly diagnosed acute embolic stroke (42 patients) and transient ischemic attack (19 patients). Computerized tomographic scanning was performed for the diagnosis of embolic stroke. Left atrial functional parameters determined by transthoracic echocardiography, such as left atrial active emptying fraction and acceleration slope of mitral inflow A wave, had significant correlations with the LAA contraction velocity (r = 0.57, p < 0.001; r = 0.54, p < 0.001, respectively). Left atrial volume index, left atrial active emptying volume and left atrial fractional shortening were also correlated with LAA contraction velocity (r = -0.44, p < 0.001; r = 0.38, p = 0.003; r = 0.37, p = 0.004, respectively). In conclusion, transthoracic echocardiography can provide valuable and reliable information about the LAA contraction velocity in stroke patients with sinus rhythm. This finding gives new insights for the appropriate strategy in the evaluation of an acute ischemic stroke.

Management of new-onset atrial fibrillation in the emergency department: is there any predictive factor for early successful cardioversion?

OBJECTIVES

The aim of this retrospective study was to assess the initial management of atrial fibrillation (AF) in the emergency department (ED) and to identify predictive factors of early conversion to sinus rhythm, which could justify a short stay in the ED observation unit (EDOU) instead of longer hospitalization.

PATIENTS AND METHODS

All patients with acute AF, either of new onset or recurrent, admitted to our hospital during a 12-month period were included in the study. Hospital records were reviewed retrospectively. The success of conversion to sinus rhythm was recorded in association with a series of clinical and laboratory factors.

RESULTS

Sixty-seven patients (39 men and 28 women), with a mean age of 63.6+/-12.2 years, were studied. The most frequent presenting symptom was palpitations (n=40, 59.7%). In forty-two patients (62.7%) the duration of symptoms was less than 48 h. Digoxine was the anti-arrhythmic agent most frequently administered (n=26, 38.8%), followed by amiodarone (n=17, 25.4%). Fifty patients (73.1%) converted to sinus rhythm and for 45 of them conversion took place during their stay in the ED or in the EDOU. Factors associated with early conversion to sinus rhythm were aged younger than 65 years (P=0.021) and symptom duration of less than 48 h (P=0.001). On the other hand, the presence of signs of heart failure was significantly associated with unsuccessful early cardioversion (P=0.001).

CONCLUSIONS

The majority of patients admitted with AF of acute onset had early conversion to sinus rhythm. AF in young patients, with a duration of symptoms of less than 48 h and without signs of heart failure can be managed in the EDOU, thus avoiding a longer hospitalization.

Clinical factors that influence response to treatment strategies in atrial fibrillation: the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study

BACKGROUND

The AFFIRM Study was a randomized multicenter comparison of 2 treatment strategies, rate-control versus rhythm-control, in high-risk patients with atrial fibrillation (AF). The primary outcome of the trial showed no overall difference in survival between strategies. However, there may be important patient subgroups for which there are identifiable differences in outcome with 1 of the 2 strategies.

METHODS AND RESULTS

Subgroups that were prespecified for analysis from the main AFFIRM Study were age, sex, coronary artery disease (CAD), hypertension, congestive heart failure (CHF), left ventricular ejection fraction (LVEF), rhythm at randomization, first episode of AF, and duration of the qualifying episode of AF. Baseline characteristics were analyzed for each subgroup. Adjusted hazard ratios for each subgroup and for each stratum were generated using Cox models, and these models were used to determine whether treatment strategy affected overall survival differentially by subgroup. Adjusted survival was worse for patients > or =65 years and for patients with a history of CHF, CAD, or an abnormal LVEF. In the adjusted analyses, the effect of treatment strategy was similar within all of the prespecified subgroups. When each subgroup stratum was analyzed separately, patients > or =65 years and patients without a history of CHF had significantly better outcome with rate-control therapy (each P < .01).

CONCLUSIONS

Overall, treatment effect for rate control versus rhythm control was the same within each subgroup. However, certain selected patient categories may have better survival with one particular strategy for management of AF.

Valsartan reduces the incidence of atrial fibrillation in patients with heart failure: results from the Valsartan Heart Failure Trial (Val-HeFT)

BACKGROUND

Atrial fibrillation (AF) in heart failure (HF) is generally considered a negative prognostic factor. Recent studies indicate that the incidence of AF might be decreased by renin angiotensin aldosterone system inhibitors. The identification of a treatment to prevent its occurrence is likely to improve patients outcome. The aims of these subanalyses of Val-HeFT were to assess (a) the effects of valsartan in the prevention of AF, (b) the independent predictors of this event, and (c) the prognostic role of AF occurrence.

METHODS AND RESULTS

The occurrence of AF was evaluated based on adverse event reports in the patients with HF enrolled in Val-HeFT. Patients were randomized to valsartan or placebo on top of their prescribed treatments for HF. During the mean 23 months of follow-up, AF was reported in 287/4395 patients (6.53%) in sinus rhythm at baseline, of whom 113/2205 (5.12%) were allocated to valsartan and 174/2190 (7.95%) to placebo (P = .0002). Multivariable analysis showed that brain natriuretic peptide (BNP) levels at baseline above the median value (HR 2.28, 95% CI 1.75-2.98), age over 70 years (HR 1.51, 95% CI 1.17-1.95), male sex (HR 1.53, 95% CI 1.07-2.18), and the valsartan treatment (HR 0.63, 95% CI 0.49-0.81) were independently associated with AF occurrence. Cox multivariable regression analysis showed that occurrence of AF was independently associated with a worse prognosis, with the adjusted hazard risks for all-cause mortality and combined mortality/morbidity of 1.40 (95% CI 1.16-1.58) and 1.38 (95% CI 1.12-1.70), respectively.

CONCLUSIONS

The results of the present study demonstrate that (a) adding valsartan to prescribed therapy for HF significantly reduces the incidence of AF by 37%; (b) BNP level and advanced age were the strongest independent predictors for AF occurrence; and (c) AF occurrence further worsens the outcome in patients with HF.

Temporal patterns of progression and regression of electrical and mechanical remodeling of the atrium

OBJECTIVES

We evaluated serial changes of electrical and mechanical parameters of atrial remodeling in dogs subjected to rapid atrial pacing.

BACKGROUND

Prolonged rapid atrial excitation causes electrical and mechanical remodeling, which contributes to persistence of atrial fibrillation and clot formation. However, the temporal relationship between these two types of atrial remodeling remains unknown.

METHODS

In 8 dogs, rapid pacing at 400 ppm was continued for 14 days. The electrophysiologic and transesophageal echocardiographic studies were performed on the day before and after 2, 7, and 14 days of rapid pacing, then 1 and 7 days after the cessation of pacing. These were compared with sham-operated dogs (instrumented but not paced, n=6).

RESULTS

With rapid pacing, there was an immediate shortening of the effective refractory period (ERP) and decreases in the transmitral atrial wave velocity (MAV) and the left atrial appendage emptying velocity (LAAV). In contrast, conduction velocity (CV) decreased and the left atrial appendage area (LAAA) increased progressively over 14 days. During the recovery, ERP, MAV, and LAAV returned to the baseline in 1 day, whereas CV and LAAA did in 7 days. ERP was highly positively correlated with LAAV (r=0.78, p<0.001) and MAV (r=0.73, p<0.001), while CV was negatively correlated only with LAAA (r=-0.58, p<0.001).

CONCLUSIONS

Pacing-induced electrical and mechanical remodeling of the atrium exhibits divergent patterns of progression and regression such that changes of ERP and contractile function take place more rapidly than those of CV and atrial size.

Atrial fibrillation

Atrial fibrillation (AF) is the most common sustained dysrhythmia in adults. It is ironic, then, that although mechanisms and effective treatments for most other supraventricular tachyarrhythmias have been discovered, AF remains incompletely understood and poorly treated. Nonetheless, our understanding of the pathophysiology of AF has improved in the last half-century, including some groundbreaking observations made in the last 10 years. Indeed, for some patients, the potential for cure now appears to be available. Because no unifying mechanism of AF has been proven, the aim of this review is to describe some of the common and important concepts behind current mechanistic theories of AF and how they contribute to our clinical understanding of AF.

Usefulness of intracardiac Doppler assessment of left atrial function immediately post-pulmonary vein antrum isolation to predict short-term recurrence of atrial fibrillation

Doppler assessments of pulmonary venous (PV) and left atrial appendage flows are useful surrogates of left atrial (LA) function, but it is unknown if these can predict atrial fibrillation (AF) recurrence after pulmonary vein antrum isolation. We compared Doppler surrogates of LA function immediately after pulmonary vein antrum isolation in patients with AF recurrence versus matched patients without recurrence. Patients with a 6-month recurrence had significantly lower LA appendage peak emptying velocity (19 +/- 10 vs 29 +/- 11 cm/s) and lower peak PV systolic wave velocity (36 +/- 17 vs 46 +/- 22 cm/s) compared with those without, suggesting that intracardiac Doppler assessment of LA function after AF ablation predicts AF recurrence.

Postfibrillatory Enhancement of Left Atrial Contractility After Short Paroxysms of Atrial Fibrillation

Implantable cardioverter defibrillators and pacemakers detect an increasing number of silent episodes of AF. In a porcine model, the study evaluated the contractility of the left atrial appendage (LAA) during AF paroxysms as they may occur in patients. Peak outflow velocity of the LA and mean outflow velocity of the LAA (LAA-V(outmean)) (n = 17) were measured before, during, and after induction of self-terminating AF. LAA-V(outmean) was also measured during incremental pacing from different atrial sites using epicardial Doppler probes (n = 6) and during continuous recordings (n = 5) of 40 minutes of pacing maintained AF. Compared to baseline sinus rhythm, LAA-V(outmean) increased during short AF episodes (41 +/- 3 vs 35 +/- 2 cm/s, P < 0.05). After termination of the AF episodes, LAA-V(outmean) further increased (69 +/- 15 cm/s, P < 0.001 vs baseline). This "postfibrillatory enhancement" maintained after repeated induction of short AF paroxysms. During prolonged AF episodes lasting 40 minutes, an initial hypercontractility (44 +/- 2 vs 38 +/- cm/s, P < 0.01) was followed by a hypocontractility after 20 minutes (29 +/- 12 P < 0.05 vs SR) and a postfibrillatory enhancement after cessation of AF (56 +/- 12 vs 27 +/- 9 cm/s at 40 minutes AF, P < 0.001). L-type Ca channel blockade abolished the initial hypercontractility during AF and the postfibrillatory enhancement. Repetitive AF paroxysms up to 2 minutes did not decrease left atrial contractility. During maintained AF up to 40 minutes an initial hypercontractility and a consecutive hypocontractility, which is overcompensated by a postfibrillatory enhancement of atrial inotropy after cessation of AF, are present. The observed phenomenon seems to be related to an increased Ca(2+) influx through the L-type Ca(2+) channel.

Automatic cardiac event recorders reveal paroxysmal atrial fibrillation after unexplained strokes or transient ischemic attacks

BACKGROUND

The etiology of stroke or transitory ischemic attack (TIA) remains frequently unknown. While paroxysmal atrial fibrillation (PAF) is often suspected, its presence remains difficult to establish. Therefore, we investigated the occurrence of PAF episodes in such a population using a long-term automatic cardiac event recorder.

METHODS

We prospectively investigated 60 consecutive subjects admitted in our university hospital for stroke (n=44) or TIA (n=16), adding long-term automatic cardiac event recorders, with a target duration of 4 days, to standard investigations, which included 12-lead ECGs and 24-hour Holter recordings.

RESULTS

In 28 patients no etiology was found for their stroke or TIA. However, one or more than one PAF episode was found in 4 of them (14.3%) using the long-term automatic event recorder. In the 32 remaining patients, 8 presented with PAF, and this was considered as the cause of their stroke. In both groups, AF was paroxysmal. The PAF episodes' duration went from 1 to 96 hours (mean +/- standard deviation, 18 hours and 30 minutes+/-30 hours).

CONCLUSIONS

Patients suffering PAF episodes after ischemic stroke or TIA were statistically less often recognized using the 24-hour Holter ECG recording alone than the R-Test Evolution alone.

Future prospects for implantable devices for atrial defibrillation

The success of the implantable cardioverter defibrillator (ICD) led to the concept of a device that would terminate atrial fibrillation (AF) using an implantable device. Implantable devices for AF are undergoing rapid evolution. Currently used devices combine pacing and cardioversion therapies to prevent and to treat AE Recent studies have shown that these devices are safe and can decrease the incidence of AF and improve quality of life significantly. Implantable devices for atrial defibrillation are likely to have an increasing role in the near future, particularly when they are used in combination with ICD and cardiac resynchronization therapy in which AF is both common and its termination is clinically beneficial.